Giant-grain silicon (GGS) and its application to stable thin-film transistor

We developed a giant-grain silicon (GGS) by Ni-mediated crystallization of amorphous silicon (a-Si) with a silicon-nitride (SiNx) cap layer. Ni particles were sputtered onto the SiNx/a-Si layer and then it was annealed at around 600 °C. The Ni diffuses through a SiNx cap and then forms NiSi2 crystallites in a-Si, which is able to induce crystallization. The grain size can be controlled from a few to 100 μm. The grain size can be increased with increasing the cap layer thickness or by decreasing the Ni density on the SiNx. The p-channel GGS poly-Si TFT exhibited a field-effect mobility of 101 cm2/Vs and a threshold voltage of −3.6 V and is very stable under gate or hot carrier bias-stress. These superior performances may be due to the smooth surface of GGS poly-Si and solid-phase crystallization of a-Si.